1. Field of the Invention
The present invention relates to vehicle powertrain control system and method.
2. Description of the Background Art
Motor vehicles are proposed, which have one powertrain including an engine, and another powertrain including an electric motor and a clutch. One powertrain is coupled with one set of road wheels. Another powertrain is coupled with another set of road wheels. Various examples of a motor vehicle of the above kind are known from JP-B2 P3062721, JP-B2 P3261673 (=U.S. Pat. No. 6,008,606) and JP-A 11-243608, respectively.
A motor vehicle disclosed in JP-B2 P3062721 includes an electric traction motor and a reduction gearing. The reduction gearing is connected to a clutch to engage and disengage the motor to and from the associated road wheels. The motor is excited only for assisting start-up of the motor vehicle. The excitation of the motor ends when the load on the motor drops after a temporary rise. The clutch disengages the motor from the road wheels after the motor vehicle has started.
A motor vehicle disclosed in JP-B2 P3261673 (=U.S. Pat. No. 6,008,606) includes an electric motor and a reduction gearing. The reduction gearing is connected to a dog clutch to engage and disengage the motor to and from the associated road wheels. The motor is excited only for assisting start-up of the motor vehicle. The excitation of the motor ends when the load on the motor drops after a temporary rise. The clutch disengages the motor from the road wheels after the motor vehicle has started.
A motor vehicle disclosed in JP-A 11-243608 includes an electric motor and a reduction gearing. The reduction gearing is connected to a clutch to engage and disengage the motor to and from the associated road wheels. To avoid shocks, according to one strategy, the motor is regulated to raise output torque gradually after engagement of the clutch. According to another strategy, the motor is regulated to increase speed to bring a revolution speed of an input shaft of the clutch into agreement with a revolution speed of an output shaft of the clutch before engagement of the clutch.
The known systems are satisfactory to some extent in enhancing vehicle start-up and/or acceleration performance by reducing shocks upon engagement of a clutch. However, a need remains for an electric motor and clutch control, which provides shock less quick response to further enhance vehicle start-up and/or acceleration performance. It appears that the known systems are not satisfactory in this respect.
An object of the present invention Is to provide vehicle powertrain system and method for enhanced start-up acceleration performance.